IntroductionHuman aging is associated with a loss of muscle, deficit in muscular strength, and impairment in performing some activities of daily life. Typically, these changes start to occur at the age of 40, and progressively worsen with aging. Sarcopenia can be defined as the natural age-related loss of muscle mass, strength and muscle function. It is estimated that 7% of adults over 70 and 20% over 80 are affected by a very debilitating sarcopenia, which costs the US health care system more than 18 billion dollars a year (Melov et al., 2007). The causes of this muscle aging are multi-factorial with theories and research suggesting it is related to oxidative stress (condition in which antioxidant levels are lower than normal), cell death, inflammation (immune response to injury or infection), hormonal dysregulation, inactivity, alternations in protein turnover and mitochondrial (the ATP energy factory in cells) dysfunction (Melov et al. 2007). Resistance training with older populations has been shown to reduce markers of oxidative stress and increase the anti-oxidant enzyme activity. Melov and colleagues investigated the question whether resistance training actually effects some of the gene expressions (see Side Bar 1 for a glossary of genetic terms) associated with muscle aging, thus reversing the aging process.

SubjectsOlder and younger samples were chosen for this study. The twenty-six older volunteers (mean age = 68 yrs) self-reported doing walking, gardening, tennis, or cycling on three or more times per week. The twenty-five younger subjects (mean age = 24 yrs) were relatively inactive, self-reporting only modest recreational activity. The researchers chose the more untrained younger population as they felt this was helpful in looking at the effects of aging and not just inactivity for their analysis. All subjects went through a medical evaluation, health history assessment, resting electrocardiogram (for detection of any heart irregular rhythms), and submaximal graded exercise test on a cycle ergometer before being admitted into the study. Subjects (all non-smokers) were excluded if they showed any orthopedic limitations to exercise, as well as evidence of heart disease or kidney problems.

Exercise Training and TestingAll subjects performed supervised resistance exercise on two non-consecutive days of the week (Monday/Thursday or Tuesday/Friday) for the 26 weeks of the study. Subjects performed 12 different exercises including the chest press, leg press, leg extension, leg flexion, shoulder press, lat pull-down, seated row, calf raise, abdominal crunch, back extension, biceps curl and triceps extension. Subjects initially began with single set training at 50% of their 1 repetition maximum (1 RM), and gradually increased to 3 sets at 80% of their 1 RM during the course of the 6-month study. The subjects retested their 1 RM for all exercises every two weeks, and the training loads were adjusted accordingly to 80% of their 1 RM. Subjects were also tested for peak maximal isometric knee extension strength of the right leg at the beginning and end of the study.

Muscle Biopsy TestingAll of the younger subjects had a muscle biopsy (incision and extraction of a small piece of muscle) taken from the vastus lateralis muscle before and after the 26-week study. All of the older population had pre-test biopsies taken while 14 of the older subjects also had post-training muscle biopsies. RNA was extracted from the muscle for analysis to determine the genes that were expressed differentially (unusually) with age.

ResultsThe researchers identified 596 differentially expressed genes (meaning atypical to other genes being analyzed). Of these, after 26 weeks of resistance training the researchers identified 179 genes associated with age and exercise showing a reversal of their gene expression. This means quite literally that the resistance training was not only slowing, but also reversing the aging process at the gene level. The gene expressions of the resistance trained older subjects demonstrated characteristics similar to those of the younger group. The researchers also noted that mitochondrial impairment, normally seen with inactivity, was reversing with the 6 months of resistance training.
In muscular strength, the peak isometric strength of the older population was initially 59% lower than the younger population. After 26 weeks of training, the older population peak strength was only 38% of the younger group.

Bottom Line Summary FindingThis novel study demonstrated that resistance training can reverse aspects of aging at the gene level. For years personal trainers and fitness professionals have exclaimed the functional movement and health benefits of resistance exercise. Now, trainers can share with their clients that regular, progressive resistance training (see Side Bar 2 for helpful tips when training mature exercises) also improves the muscle's longevity profile at the molecular level. It is well known that long-term resistance training is associated with a lower risk to age-associated morbidity and mortality. This original study may be a first step in explaining how some of these positive changes occur.

Side Bar 1. Definitions of Selected Terms of Genetics The following is a brief glossary of selected genetic terms.
DNA (deoxyribonucleic acid): A group of complex compounds found in all living cells that carries the genetic information in the cell and is capable of self-replication, and synthesis of RNA.

Gene: A small piece of DNA, which instructs the body how to build a specific protein. There are approximately 30,000 genes in each cell of the human body.

Gene expression: The conversion of the information encoded in a gene first into messenger RNA and then to a protein.

Messenger RNA: The form of RNA that mediates the transfer of genetic information from the cell nucleus to ribosomes in the cytoplasm, where it serves as a template for protein synthesis.

RNA (Ribonucleic acid): A chemical found in the nucleus and cytoplasm of cells that plays an important role in protein synthesis and other chemical activities of the cell.

Translation: The first stage in the process in which cells build proteins.

Transcription: The process by which messenger RNA is synthesized from a DNA template, resulting in the transfer of genetic information from the DNA molecule to the messenger RNA.End

Side Bar 2: 10 Training Tips for Mature ClientsThe following are 10 helpful training guidelines when working with mature exercisers.

1) Teaching correct lifting mechanics should be a priority with all personal trainers working with mature clients.

2) Many older individuals do not understand the concept of progressive overload, and must be educated and directed properly.

3) Always have clients perform exercises in a pain-free range of motion with controlled joint movements.

4) Keep breathing patterns normal during resistance exercises. Encourage the client to exhale during the more challenging part of the exercise. For instance, when doing a squat, inhale on the descent of the squat and exhale on the assent against gravity. Breath holding during resistance exercise may elevate intra thoracic pressures dangerously high, placing undue stress on the heart.

5) Begin resistance training programs with minimal training loads to allow adequate time for the joint(s) and associated connective tissues to adjust to the loads.

6) Avoid excessive resistance training loads or repetition of loads as this may aggravate a pre-existing health condition. Clients with arthritis and other joint and bone disorders should not be advised to do resistance during periods of pain or inflammation.

7) Since eccentric training (lengthening muscle actions) has been shown to result in greater muscle soreness, the use of eccentric training in mature populations should be done with carefulness.

8) When re-starting a resistance training regimen from a break or leave of absence, have clients begin with loads that are approximately 50% or less of the previous training intensity.

9) To help mature clients develop better balance and muscle coordination, perform several exercise in a standing position with free weights and other exercise props, such as medicine balls.

10) Plan workout time efficiently for the mature client. Sessions lasting over 60 minutes may be too fatiguing. In addition, training sessions that are too long may be disadvantageous to overall exercise adherence.